Coated microcapsules

ABSTRACT

Accordingly, there are provided coated microcapsules including: a microcapsule including a polymeric shell and a liquid core material encapsulated therein; and a metallic coating surrounding said microcapsule, wherein the metallic coating comprises particles of a first metal adsorbed on said polymeric shell and a film of a second metal formed thereon; wherein said particles of the first metal are charge-stabilized nanoparticles; processes for preparing the coated microcapsules, as well as formulations related thereto are also included.

FIELD

The present disclosure relates to microcapsules including a liquid corematerial, to processes for their preparation and to formulationsincluding the same. More particularly, the present disclosure relates tomicrocapsules including a liquid core material that can be released in acontrolled manner during use. The microcapsules find application in finefragrance formulations and other consumer products where controlledrelease of active ingredients is desired.

BACKGROUND

The encapsulation of liquid substances and their controlled, targeteddelivery is important to industry. However, the efficient encapsulationof liquid substances, especially volatile substances, has provendifficult. Although applications of encapsulation techniques areincreasing year on year, there remain significant shortcomings andlimitations. In particular, the encapsulation of volatile compounds isan area in which little progress has been made.

Particular problems are encountered in the encapsulation of perfumeoils, which are volatile substances found in fine fragrances and otherfragrance formulations. Although the use of microcapsules to encapsulateperfume oils has been proposed, fragrance formulations typically containpolar solvents such as ethanol in which the microcapsules are dispersed.These polar solvents can readily penetrate the wall of themicrocapsules, causing the perfume oils to leach prematurely from themicrocapsules. It would be desirable to provide microcapsules whichenable perfume oils to be released in a controlled manner during use,e.g. by rupturing the microcapsules during normal human movement.

There is a need in the art for improved microcapsules for encapsulatingliquid substances, especially microcapsules which exhibit an improvedrelease profile. In particular, there is a need for microcapsules forencapsulating liquid substances such as perfume oils, wherein themicrocapsules are substantially impermeable to polar solvents such asethanol yet, at the same time, are capable of releasing their contentsin a controlled manner during use. There is also a need for improvedprocesses for the preparation of microcapsules.

SUMMARY

Accordingly, there is provided a coated microcapsule comprising:

a microcapsule comprising a polymeric shell and a liquid core materialencapsulated therein; and

a metallic coating surrounding said microcapsule, wherein the metalliccoating comprises particles of a first metal adsorbed on said polymericshell and a film of a second metal formed thereon;

wherein said particles of the first metal are charge-stabilisednanoparticles.

Accordingly, there is provided a process for preparing a coatedmicrocapsule, the process comprising:

providing a microcapsule comprising a polymeric shell and a liquid corematerial encapsulated therein; and

coating said microcapsule with a metallic coating which surrounds saidmicrocapsule; wherein the step of coating said microcapsule comprises:

adsorbing particles of a first metal on said polymeric shell; and

forming a film of a second metal on said particles of the first metal;

wherein said particles are charge-stabilised nanoparticles.

The present disclosure also provides precursors suitable for preparingthe coated microcapsules. In other aspects, the present disclosureprovides a plurality of coated microcapsules, as well as formulationscomprising the same. Also provided are methods of fragrancing asubstrate using a coated microcapsule.

The coated microcapsules offer various advantages and benefits. Inparticular, volatile liquid substances such as perfume oils can beencapsulated in microcapsules which are substantially impermeable topolar solvents such as ethanol yet, at the same time, can be rupturedduring use. Moreover, the preparation processes disclosed herein enablethe coated microcapsules to be prepared in a facile manner. Inparticular, the processes described herein may enable a metallic coatingto be applied in only a small number of steps.

BRIEF DESCRIPTION OF THE DRAWINGS

FIGS. 1A, 1B, 1C and 1D depict a schematic diagram illustrating aprocess for preparing an exemplary coated microcapsule wherein aschematic diagram is in the upper portion and beneath the schematicdiagram is the corresponding microscopy. The upper schematic diagramillustrates a process for preparing an exemplary coated microcapsule.The emulsion template (FIG. 1A) is converted to an uncoated microcapsule(FIG. 1B) comprising a polymeric shell and a liquid core material.Particles of a first metal are adsorbed onto the microcapsule surface(FIG. 1C) and a continuous film of a second metal is then applied,yielding a coated microcapsule (FIG. 1D). Shown beneath the schematicdiagram are corresponding optical microscopy (FIG. 1A), transmissionelectron microscopy (TEM) (FIG. 1B, FIG. 1C) and scanning electronmicroscopy (SEM) (FIG. 1D) images of a microcapsule formed by such aprocess.

FIGS. 2A, 2B, 2C, 2D and 2E provide optical, SEM and TEM images obtainedat various stages of preparation of a coated microcapsule, themicrocapsule comprising a PEMA shell, a toluene core and a metalliccoating comprising a continuous silver film formed on a layer ofborohydride-stabilised gold nanoparticles. Shown are: FIG. 2A an opticalimage showing the uncoated microcapsules; 2B and 2C TEM images showingthe borohydride-stabilised gold nanoparticles adsorbed on the surface ofthe microcapsules; and 2D an SEM image showing the continuous silverfilm. Also shown is: 2E an EDX graph indicating the silver content ofthe metallic film.

FIGS. 3A, 3B, 3C, 3D, and 3E are a series of TEM images showing metallicfilms of varying thicknesses.

FIG. 4 is a graph to illustrate that the thickness of the metalliccoating may be modified by varying the concentration of silver ions inthe electroless plating solution.

DESCRIPTION OF VARIOUS EMBODIMENTS

Liquid Core Material

The coated microcapsules may comprise a liquid core materialencapsulated by a polymeric shell. The term “liquid core material” asused herein refers to a core material formed of one or more components,at least 90% by weight of which are liquid at standard ambienttemperature and pressure. The term “standard ambient temperature andpressure” (or “STP”) refers to a temperature of 25° C. and an absolutepressure of 100 kPa. Preferably, the liquid core material comprises atleast 95% by weight, e.g. at least 98% by weight, of one or morecomponents which are liquid at standard ambient temperature andpressure. In some examples, the liquid core material consists of one ormore components which are liquid at standard ambient temperature andpressure. In some examples, the liquid core material includes a mixtureof liquids and a solid, non-limiting examples of which include a mixtureof vanillin and perfume oils.

The liquid core material may be present in the coated microcapsule in anamount of at least 1% by weight of the microcapsule, preferably in anamount of at least 30% by weight, and more preferably in an amount of atleast 60% by weight. In some examples, the liquid core material ispresent in the coated microcapsule in an amount of from 10 to 99.9% byweight of the coated microcapsule, alternatively from 40 to 90% byweight of the coated microcapsule, alternatively from 50 to 90% byweight, alternatively from 60 to 80% by weight.

In some examples, the liquid core material comprises one or morecomponents which are volatile. Unless otherwise specified, the term“volatile” as used herein refers to those materials that are liquid orsolid under ambient conditions and which have a measurable vapourpressure at 25° C. These materials typically have a vapour pressure ofgreater than about 0.0000001 mm Hg, e.g. from about 0.02 mm Hg to about20 mm Hg, and an average boiling point typically less than about 250°C., e.g. less than about 235° C.

The liquid core material may consist of a single material or it may beformed of a mixture of different materials. In some examples, the liquidcore material comprises one or more active ingredients. The coatedmicrocapsules described herein are useful with a wide variety of activeingredients (i.e. “core materials”) including, by way of illustrationand without limitation, perfumes; brighteners; insect repellants;silicones; waxes; flavors; vitamins; fabric softening agents;depilatories; skin care agents; enzymes; probiotics; dye polymerconjugate; dye clay conjugate; perfume delivery system; sensates in oneaspect a cooling agent; attractants, in one aspect a pheromone;anti-bacterial agents; dyes; pigments; bleaches; flavorants; sweeteners;waxes; pharmaceuticals; fertilizers; herbicides and mixtures thereof.The microcapsule core materials can include materials which alterrheology or flow characteristics, or extend shelf life or productstability. Essential oils as core materials can include, for example, byway of illustration wintergreen oil, cinnamon oil, clove oil, lemon oil,lime oil, orange oil, peppermint oil and the like. Dyes can includefluorans, lactones, indolyl red, I6B, leuco dyes, all by way ofillustration and not limitation. Particularly useful are encapsulatedmaterials such as volatile fragrances and flavorants.

The liquid core material preferably comprises one or more componentswhich are oil-soluble. The use of a liquid core material which isoil-soluble will be preferable having regard to, inter alia, theproduction of the microcapsules, which will typically be prepared by aprocess which involves the use of an oil-in-water emulsion in which theliquid core material is present in the non-aqueous (oil) phase. In someexamples, the liquid core material is substantially free of water. Inparticular, the amount of water present in the liquid core material maybe less than 5% by weight, e.g. less than 1% by weight, of the liquidcore material. More preferably, the liquid core material consists of oneor more oil-soluble components.

The liquid core material is preferably free of compounds which arecapable of reacting with any of the compounds that are used to form thepolymeric shell of the microcapsules. In particular, the liquid corematerial is preferably free of any polymerisable compounds.

In some examples, the liquid core material comprises a perfume oilformed of one or more perfume raw materials. The term “perfume oil” asused herein refers to the perfume raw material, or mixture of perfumeraw materials, that is used to impart an overall pleasant odour profileto the liquid core material. Thus, where different perfume raw materialsare present in the liquid core material, this term refers to the overallmixture of perfume raw materials in the liquid core material. The choiceof the perfume raw materials defines both the odour intensity andcharacter of the liquid core material. The perfume oils utilised in thecoated microcapsules may be relatively simple in their chemical make-up,for example consisting of only a single perfume raw material, or theymay comprise complex mixtures of perfume raw materials, all chosen toprovide a desired odour.

The perfume oil may comprise one or more perfume raw materials having aboiling point of less than 500° C., e.g. less than 400° C., e.g. lessthan 350° C. The boiling points of many perfume raw materials are givenin, e.g., “Perfume and Flavor Chemicals (Aroma Chemicals)” by SteffenArctander (1969) and other textbooks known in the art.

The one or more perfume raw materials will typically be hydrophobic. Thehydrophobicity of a given compound may be defined in terms of itspartition coefficient. The term “partition coefficient” as used hereinrefers to the ratio between the equilibrium concentration of thatsubstance in n-octanol and in water, and is a measure of thedifferential solubility of said substance between these two solvents.Partition coefficients are described in more detail in U.S. Pat. No.5,578,563.

The term “log P” refers to the logarithm to the base 10 of the partitioncoefficient. Values of log P values can be readily calculated using aprogram called “C LOG P” which is available from Daylight ChemicalInformation Systems Inc., 30 Irvine Calif., U.S.A. or using AdvancedChemistry Development (ACD/Labs) Software 13375P 9 V11.02 (© 1994-2014ACD/Labs).

In some examples, the perfume oil comprises one or more perfume rawmaterials having a calculated log P (C log P) value of about −0.5 orgreater, e.g. greater than 0.1, e.g. greater than 0.5, e.g. greater than1.0. In some examples, the perfume oil consists of one or more perfumeraw materials having a C log P value of greater than 0.1, e.g. greaterthan 0.5, e.g. greater than 1.0.

In some examples, the perfume oil comprises one or more perfume rawmaterials selected from aldehydes, esters, alcohols, ketones, ethers,alkenes, nitriles, Schiff bases, and mixtures thereof.

Examples of aldehyde perfume raw materials include, without limitation,alpha-amylcinnamaldehyde, anisic aldehyde, decyl aldehyde, lauricaldehyde, methyl n-nonyl acetaldehyde, methyl octyl acetaldehyde,nonylaldehyde, benzenecarboxaldehyde, neral, geranial,1,1-diethoxy-3,7-dimethylocta-2,6-diene, 4-isopropylbenzaldehyde,2,4-dimethyl-3-cyclohexene-1-carboxaldehyde,alpha-methyl-p-isopropyldihydrocinnamaldehyde, 3-(3-isopropylphenyl)butanal, alpha-hexylcinnamaldehyde, 7-hydroxy-3,7-dimethyloctan-1-al,2,4-dimethyl-3-cyclohexene-1-carboxaldehyde, octyl aldehyde,phenylacetaldehyde, 2,4-dimethyl-3-cyclohexene-1-carboxaldehyde,hexanal, 3,7-dimethyloctanal,6,6-dimethylbicyclo[3.1.1]hept-2-ene-2-butanal, nonanal, octanal,2-nonenal undecenal,2-methyl-4-(2,6,6-trimethyl-1-cyclohexenyl-1)-2-butenal,2,6-dimethyloctanal, 3-(p-isopropylphenyl)propionaldehyde,3-phenyl-4-pentenal citronellal, o/p-ethyl-alpha, alpha, 9-decenal,dimethyldihydrocinnamaldehyde, p-isobutyl-alphamethylydrocinnamaldehyde,cis-4-decen-1-al, 2,5-dimethyl-2-ethenyl-4-hexenal,trans-2-methyl-2-butenal, 3-methylnonanal, alpha-sinensal,3-phenylbutanal, 2,2-dimethyl-3-phenylpropionaldehyde,m-tertbutyl-alpha-methyldihydrocinnamic aldehyde, geranyloxyacetaldehyde, trans-4-decen-1-al, methoxycitronellal, and mixturesthereof.

Examples of ester perfume raw materials include, without limitation,allyl cyclohexane-propionate, allyl heptanoate, allyl amyl glycolate,allyl caproate, amyl acetate (n-pentyl acetate), amyl propionate, benzylacetate, benzyl propionate, benzyl salicylate, cis-3-hexenylacetate,citronellyl acetate, citronellyl propionate, cyclohexyl salicylate,dihydro isojasmonate, dimethyl benzyl carbinyl acetate, ethyl acetate,ethyl acetoacetate, ethyl butyrate, ethyl-2-methyl butyrate,ethyl-2-methyl pentanoate, fenchyl acetate(1,3,3-trimethyl-2-norbornanyl acetate), tricyclodecenyl acetate,tricyclodecenyl propionate, geranyl acetate, cis-3-hexenyl isobutyrate,hexyl acetate, cis-3-hexenyl salicylate, n-hexyl salicylate, isobornylacetate, linalyl acetate, p-t-butyl cyclohexyl acetate, (−)-L-menthylacetate, o-t-butylcyclohexyl acetate, methyl benzoate, methyl dihydroisojasmonate, alpha-methylbenzyl acetate, methyl salicylate,2-phenylethyl acetate, prenyl acetate, cedryl acetate, cyclabute,phenethyl phenylacetate, terpinyl formate, citronellyl anthranilate,ethyl tricyclo[5.2.1.0-2,6]decane-2-carboxylate, n-hexyl ethylacetoacetate, 2-tertbutyl-4-methyl cyclohexyl acetate, formic acid,3,5,5-trimethylhexyl ester, phenethyl crotonate, cyclogeranyl acetate,geranyl crotonate, ethyl geranate, geranyl isobutyrate,3,7-dimethyl-ethyl 2-nonynoate-2,6-octadienoic acid methyl ester,citronellyl valerate, 2-hexenylcyclopentanone, cyclohexyl anthranilate,L-citronellyl tiglate, butyl tiglate, pentyl tiglate, geranyl caprylate,9-decenyl acetate, 2-isopropyl-5-methylhexyl-1 butyrate, n-pentylbenzoate, 2-methylbutyl benzoate (and mixtures thereof with pentylbenzoate), dimethyl benzyl carbinyl propionate, dimethyl benzyl carbinylacetate, trans-2-hexenyl salicylate, dimethyl benzyl carbinylisobutyrate, 3,7-dimethyloctyl formate, rhodinyl formate, rhodinylisovalerate, rhodinyl acetate, rhodinyl butyrate, rhodinyl propionate,cyclohexylethyl acetate, neryl butyrate, tetrahydrogeranyl butyrate,myrcenyl acetate, 2,5-dimethyl-2-ethenylhex-4-enoic acid, methyl ester,2,4-dimethylcyclohexane-1-methyl acetate, ocimenyl acetate, linalylisobutyrate, 6-methyl-5-heptenyl-1 acetate, 4-methyl-2-pentyl acetate,n-pentyl 2-methylbutyrate, propyl acetate, isopropenyl acetate,isopropyl acetate, 1-methylcyclohex-3-ene-carboxylic acid, methyl ester,propyl tiglate, propyl/isobutyl cyclopent-3-enyl-1-acetate (alphavinyl),butyl 2-furoate, ethyl 2-pentenoate, (E)-methyl 3-pentenoate,3-methoxy-3-methylbutyl acetate, n-pentyl crotonate, n-pentylisobutyrate, propyl formate, furfuryl butyrate, methyl angelate, methylpivalate, prenyl caproate, furfuryl propionate, diethyl malate,isopropyl 2-methylbutyrate, dimethyl malonate, bornyl formate, styralylacetate, 1-(2-furyl)-1-propanone, 1-citronellyl acetate,3,7-dimethyl-1,6-nonadien-3-yl acetate, neryl crotonate, dihydromyrcenylacetate, tetrahydromyrcenyl acetate, lavandulyl acetate, 4-cyclooctenylisobutyrate, cyclopentyl isobutyrate, 3-methyl-3-butenyl acetate, allylacetate, geranyl formate, cis-3-hexenyl caproate, and mixtures thereof.

Examples of alcohol perfume raw materials include, without limitation,benzyl alcohol, beta-gamma-hexenol (2-hexen-1-ol), cedrol, citronellol,cinnamic alcohol, p-cresol, cumic alcohol, dihydromyrcenol,3,7-dimethyl-1-octanol, dimethyl benzyl carbinol, eucalyptol, eugenol,fenchyl alcohol, geraniol, hydratopic alcohol, isononyl alcohol(3,5,5-trimethyl-1-hexanol), linalool, methyl chavicol (estragole),methyl eugenol (eugenyl methyl ether), nerol, 2-octanol, patchoulialcohol, phenyl hexanol (3-methyl-5-phenyl-1-pentanol), phenethylalcohol, alpha-terpineol, tetrahydrolinalool, tetrahydromyrcenol,4-methyl-3-decen-5-ol, 1-3,7-dimethyloctane-1-ol,2-(furfuryl-2)-heptanol, 6,8-dimethyl-2-nonanol, ethyl norbornylcyclohexanol, beta-methyl cyclohexane ethanol,3,7-dimethyl-(2),6-octen(adien)-1-ol, trans-2-undecen-1-ol,2-ethyl-2-prenyl-3-hexenol, isobutyl benzyl carbinol, dimethyl benzylcarbinol, ocimenol, 3,7-dimethyl-1,6-nonadien-3-ol (cis & trans),tetrahydromyrcenol, alpha-terpineol, 9-decenol-1,2-(2-hexenyl)-cyclopentanol, 2,6-dimethyl-2-heptanol,3-methyl-1-octen-3-ol, 2,6-dimethyl-5-hepten-2-ol,3,7,9-trimethyl-1,6-decadien-3-ol, 3,7-dimethyl-6-nonen-1-ol,3,7-dimethyl-1-octyn-3-ol, 2,6-dimethyl-1,5,7-octatrienol-3,dihydromyrcenol, 2,6,-trimethyl-5,9-undecadienol,2,5-dimethyl-2-propylhex-4-enol-1, (Z)-3-hexenol,o,m,p-methyl-phenylethanol, 2-methyl-5-phenyl-1-pentanol,3-methylphenethyl alcohol, para-methyl dimethyl benzyl carbinol, methylbenzyl carbinol, p-methylphenylethanol, 3,7-dimethyl-2-octen-1-ol,2-methyl-6-methylene-7-octen-4-ol, and mixtures thereof.

Examples of ketone perfume raw materials include, without limitation,oxacycloheptadec-10-en-2-one, benzylacetone, benzophenone, L-carvone,cis-jasmone, 4-(2,6,6-trimethyl-3-cyclohexen-1-yl)-but-3-en-4-one, ethylamyl ketone, alpha-ionone, ionone beta, ethanone,octahydro-2,3,8,8-tetramethyl-2-acetonaphthalene, alpha-irone,1-(5,5-dimethyl-1-cyclo-hexen-1-yl)-4-penten-1-one, 3-nonanone, ethylhexyl ketone, menthone, 4-methyl-acetophenone, gamma-methyl ionone,methyl pentyl ketone, methyl heptenone (6-methyl-5-hepten-2-one), methylheptyl ketone, methyl hexyl ketone, delta muscenone, 2-octanone,2-pentyl-3-methyl-2-cyclopenten-1-one, 2-heptylcyclopentanone,alpha-methylionone, 3-methyl-2-(trans-2-pentenyl)-cyclopentenone,octenyl cyclopentanone, n-amylcyclopentenone,6-hydroxy-3,7-dimethyloctanoic acid lactone,2-hydroxy-2-cyclohexen-1-one, 3-methyl-4-phenyl-3-buten-2-one,2-pentyl-2,5,5-trimethylcyclopentanone, 2-cyclopentylcyclopentanol-1,5-methylhexan-2-one, gamma-dodecalactone, delta-dodecalactonedelta-dodecalactone, gamma-nonalactone, delta-nonalactone,gamma-octalactone, delta-undecalactone, gamma-undecalactone, andmixtures thereof.

Examples of ether perfume raw materials include, without limitation,p-cresyl methyl ether,4,6,6,7,8,8-hexamethyl-1,3,4,6,7,8-hexahydro-cyclopenta(G)-2-benzopyran,beta-naphthyl methyl ether, methyl isobutenyl tetrahydropyran,5-acetyl-1,1,2,3,3,6-hexamethylindan (phantolide),7-acetyl-1,1,3,4,4,6-hexamethyltetralin (tonalid),2-phenylethyl-3-methylbut-2-enyl ether, ethyl geranyl ether, phenylethylisopropyl ether, and mixtures thereof.

Examples of alkene perfume raw materials include, without limitation,allo-ocimene, camphene, beta-caryophyllene, cadinene, diphenylmethane,d-limonene, lymolene, beta-myrcene, para-cymene, 2-alpha-pinene,beta-pinene, alpha-terpinene, gamma-terpinene, terpineolene,7-methyl-3-methylene-1,6-octadiene, and mixtures thereof.

Examples of nitrile perfume raw materials include, without limitation,3,7-dimethyl-6-octenenitrile, 3,7-dimethyl-2(3), 6-nonadienenitrile,(2E,6Z)-2,6-nonadienenitrile, n-dodecane nitrile, and mixtures thereof.

Examples of Schiff base perfume raw materials include, withoutlimitation, citronellyl nitrile, nonanal/methyl anthranilate,N-octylidene-anthranilic acid methyl ester, hydroxycitronellal/methylanthranilate, cyclamen aldehyde/methyl anthranilate,methoxyphenylpropanal/methyl anthranilate, ethylp-aminobenzoate/hydroxycitronellal, citral/methyl anthranilate,2,4-dimethylcyclohex-3-enecarbaldehyde methyl anthranilate,hydroxycitronellal-indole, and mixtures thereof.

Non-limiting examples of other the perfume raw materials useful hereininclude pro-fragrances such as acetal pro-fragrances, ketalpro-fragrances, ester pro-fragrances, hydrolyzable inorganic-organicpro-fragrances, and mixtures thereof. The fragrance materials may bereleased from the pro-fragrances in a number of ways. For example, thefragrance may be released as a result of simple hydrolysis, or by ashift in an equilibrium reaction, or by a pH-change, or by enzymaticrelease.

In some examples, the perfume oil comprises one or more of the perfumeraw materials recited in the above lists. In some examples, the perfumeoil comprises a plurality of perfume raw materials recited in the abovelists.

In some examples, the liquid core material comprises one or more perfumeoils of natural origin. In some examples, the liquid core materialcomprises one or more perfume oils selected from musk oil, civet,castoreum, ambergris, nutmeg extract, cardamom extract, ginger extract,cinnamon extract, patchouli oil, geranium oil, orange oil, mandarin oil,orange flower extract, cedarwood, vetyver, lavandin, ylang extract,tuberose extract, sandalwood oil, bergamot oil, rosemary oil, spearmintoil, peppermint oil, lemon oil, lavender oil, citronella oil, chamomileoil, clove oil, sage oil, neroli oil, labdanum oil, eucalyptus oil,verbena oil, mimosa extract, narcissus extract, carrot seed extract,jasmine extract, olibanum extract, rose extract, and mixtures thereof.One or more of these perfume oils may be used with one or more of theperfume raw materials recited above.

The perfume oil may be present in the liquid core material in an amountof from 0.1 to 100% by weight of the liquid core material. In someexamples, the liquid core material consists essentially, e.g. consistsof, a perfume oil. In some examples, the perfume oil is present in theliquid core material in an amount of at least 10% by weight of theliquid core material, preferably at least 20% by weight, and morepreferably at least 30% by weight. In some examples, the perfume oil ispresent in the liquid core material in an amount of from 80-100% byweight of the liquid core material, alternatively less than 80% byweight of the liquid core material, alternatively less than 70% byweight, alternatively less than 60% by weight. In some examples, theperfume oil is present in an amount of from 10 to 50% by weight of theliquid core material, more preferably from 15 to 30%. Preferred liquidcore materials contain from 10 to 80% by weight of a perfume oil,preferably from 20 to 70%, more preferably from 30 to 60%.

The liquid core material may comprise one or more components in additionto the perfume oil. For example, the liquid core material may compriseone or more diluents. Examples of diluents include mono-, di- andtri-esters of C₄-C₂₄ fatty acids and glycerine, isopropyl myristate,soybean oil, hexadecanoic acid, methyl ester, isododecane, and mixturesthereof. Where present, diluents are preferably present in the liquidcore material in an amount of at least 1% by weight of the liquid corematerial, e.g. from 10 to 60% by weight of the liquid core material.

Polymeric Shell

The liquid core material is encapsulated by a polymeric shell. Thecoated microcapsules may be prepared by first forming the polymericshell around the liquid core material to as to form an uncoatedmicrocapsule, and subsequently forming the metallic coating. The term“uncoated microcapsule” as used herein refers to the microcapsulecomprising the liquid core material prior to coating with the metalliccoating.

The polymeric shell may comprise one or more polymeric materials. Forexample, the polymeric shell may comprise one or more polymers chosenfrom synthetic polymers, naturally-occurring polymers, and combinationsthereof. Examples of synthetic polymers include, without limitation,nylon, polyethylenes, polyamides, polystyrenes, polyisoprenes,polycarbonates, polyesters, polyureas, polyurethanes, polyolefins,polysaccharides, epoxy resins, vinyl polymers, polyacrylates, andcombinations thereof. Examples of synthetic polymers include, withoutlimitation, silk, wool, gelatin, cellulose, alginate, proteins, andcombinations thereof. The polymeric shell may comprise a homopolymer ora copolymer (e.g. a block copolymer or a graft copolymer).

In some examples, the polymeric shell comprises a polyacrylate, e.g.poly(methyl methacrylate) (PMMA) or poly(ethyl methacrylate) (PEMA). Thepolyacrylate may be present in an amount of at least 5%, at least 10%,at least 25%, at least 30%, at least 50%, at least 70%, or at least 90%of the weight of the polymeric shell.

In some examples, the polymeric shell comprises a polyacrylate randomcopolymer. For example, the polyacrylate random copolymer can comprise:an amine content of from 0.2 to 2.0% by weight of the total polyacrylatemass; a carboxylic acid content of from 0.6 to 6.0% by weight of thetotal polyacrylate mass; and a combination of an amine content of from0.1 to 1.0% and a carboxylic acid content of from 0.3 to 3.0% by weightof the total polyacrylate mass.

In some examples, the microcapsule shell comprises a reaction product ofa first mixture in the presence of a second mixture comprising anemulsifier, the first mixture comprising a reaction product of i) an oilsoluble or dispersible amine with ii) a multifunctional acrylate ormethacrylate monomer or oligomer, an oil soluble acid and an initiator,the emulsifier comprising a water soluble or water dispersible acrylicacid alkyl acid copolymer, an alkali or alkali salt, and optionally awater phase initiator. In some examples, said amine is selected from thegroup consisting of aminoalkyl acrylates, alkyl aminoalkyl acrylates,dialkyl aminoalkyl acrylates, aminoalkyl methacrylates, alkylaminoaminoalkyl methacrylates, dialkyl aminoalkyl methacrylates,tertiarybutyl aminoethyl methacrylates, diethylaminoethyl methacrylates,dimethylaminoethyl methacrylates, dipropylaminoethyl methacrylates, andmixtures thereof. In some examples, said amine is an aminoalkyl acrylateor aminoalkyl methacrylate.

In some examples, the polymeric shell comprises a reaction product of anamine with an aldehyde. For example, the polymeric shell may comprise areaction product selected from urea cross-linked with formaldehyde orglutaraldehyde; melamine cross-linked with formaldehyde;gelatin-polyphosphate coacervates optionally cross-linked withgluteraldehyde; gelatin-gum arabic coacervates; cross-linked siliconefluids; polyamines reacted with polyisocyanates; acrylate monomerspolymerized via free radical polymerization, and mixtures thereof. Insome examples, the polymeric shell comprises a reaction product selectedfrom urea-formaldehyde (i.e. the reaction product of urea cross-linkedwith formaldehyde) and melamine resin (i.e. melamine cross-linked withformaldehyde).

In some examples, the polymeric shell comprises gelatin, optionally incombination with one or more additional polymers. In some examples, thepolymeric shell comprises gelatin and polyurea.

The polymeric shell may comprise one or more components in addition tothe one or more wall-forming polymers. Preferably, the polymeric shellfurther comprises an emulsifier. In this regard, and as described inmore detail below, encapsulation of the liquid core material may beachieved by providing an oil-in-water emulsion in which droplets of anoil (non-aqueous) phase comprising the liquid core material aredispersed in a continuous aqueous phase, and then forming a polymericshell around the droplets. Such processes are typically performed in thepresence of an emulsifier (also known as a stabiliser), which stabilisesthe emulsion and reduce the likelihood of aggregation of microcapsulesduring formation of the polymeric shell. Emulsifiers normally stabilisethe emulsion by orienting themselves at the oil phase/aqueous phaseinterface, thus establishing a steric and/or charged boundary layeraround each droplet. This layer serves as a barrier to other particlesor droplets preventing their intimate contact and coalescence, therebymaintaining a uniform droplet size. Since the emulsifier will typicallybe retained in the polymeric shell, the polymeric shell of themicrocapsules may comprise an emulsifier as an additional component. Theemulsifier may be adsorbed on and/or absorbed in the polymeric shell ofthe microcapsules.

The emulsifier may be a polymer or a surfactant. The emulsifier may be anon-ionic, cationic, anionic, zwitterionic or amphoteric emulsifier.Examples of suitable emulsifiers include, without limitation, cetyltrimethylammonium bromide (CTAB), poly(vinyl alcohol) (PVA), poly(vinylpyrrolidone) (PVP), poly(acrylic acid) (PAA), poly(methacrylic acid)(PMA), dodecyldimethyl ammonium bromide (DDAB), sodium dodecyl sulfate(SDS) and poly(ethylene glycol). In some examples, the emulsifier isselected from cetyl trimethylammonium bromide, poly(vinyl alcohol) andpoly(vinyl pyrrolidone).

The uncoated microcapsules may be formed by emulsifying the liquid corematerial into droplets and forming a polymeric shell around thedroplets. Microencapsulation of the liquid core material can beconducted using a variety of methods known in the art, includingcoacervation methods, in situ polymerisation methods and interfacialpolymerisation methods. Such techniques are known in the art (see, e.g.,“Microencapsulation: Methods and Industrial Applications”, Edited byBenita and Simon, Marcel Dekker, Inc., 1996; U.S. Pat. No. 2,730,456;U.S. Pat. No. 2,800,457; U.S. Pat. No. 2,800,458; U.S. Pat. No.4,552,811; U.S. Pat. No. 6,592,990; and U.S. 2006/0263518).

In some examples, the microcapsules are prepared a coacervation methodwhich involves oil-in-water emulsification followed by solventextraction. Such procedures are known in the art (see, e.g., Loxley etal., Journal of Colloid and Interface Science, vol. 208, pp. 49-62,1998) and involve the use of a non-aqueous phase comprising a polymericmaterial that is capable of forming a polymeric shell, a poor solventfor the polymeric material, and a co-solvent which is a good solvent forthe polymeric material. The non-aqueous and aqueous phases areemulsified, forming an oil-in-water emulsion comprising droplets of thenon-aqueous phase dispersed in the continuous aqueous phase. Theco-solvent is then partially or wholly extracted from the non-aqueousphase, causing the polymeric material to precipitate around the poorsolvent, thereby encapsulating the poor solvent.

Thus, the uncoated microcapsules may be prepared by: (i) providing anon-aqueous phase comprising a polymeric material that is capable offorming a polymeric shell, a liquid core material which is a poorsolvent for the polymeric material, and a co-solvent which is a goodsolvent for the polymeric material; (ii) providing an aqueous phase;(iii) emulsifying the non-aqueous phase and the aqueous phase to form anemulsion comprising droplets of the non-aqueous phase dispersed withinthe aqueous phase; and (iv) extracting at least a portion of theco-solvent from the non-aqueous phase such that the polymeric materialprecipitates around droplets comprising the liquid core material,thereby encapsulating the liquid core material.

In some examples, the polymeric material comprises a polyacrylate, e.g.poly(methyl methacrylate) (PMMA), poly(ethyl methacrylate) (PEMA) or acombination thereof. In some examples, the polymeric material consistsof poly(methyl methacrylate) (PMMA) or poly(ethyl methacrylate) (PEMA).

Preferably, the polymeric material has a weight average molecular weightof at least 10 kDa, more preferably at least 50 kDa, more preferably atleast 100 kDa. Preferably, the polymeric material has a weight averagemolecular weight of from 10 to 1000 kDa, more preferably from 50 to 800kDa, more preferably from 100 to 600 kDa.

With regard to the chemical composition of the non-aqueous phase, theliquid core material is preferably present in an amount of from 0.5 to50%, preferably from 1 to 45%, and more preferably from 3 to 40% byweight of the non-aqueous phase. The polymeric material is preferablypresent in the non-aqueous phase in an amount of from 0.5 to 15%,preferably from 1 to 10%, and more preferably from 2 to 8% by weight ofthe non-aqueous phase. The co-solvent is preferably present in an amountof from 40 to 98%, preferably from 50 to 98%, and more preferably from60 to 95% by weight of the non-aqueous phase. In some examples, thenon-aqueous phase consists of the liquid core material, the polymericmaterial and the co-solvent.

In some examples, the co-solvent is a volatile material, e.g.dichloromethane (DCM), and is extracted from the non-aqueous phase byevaporation. In this case, precipitation of the polymeric material maybe aided by heating the emulsion to promote evaporation of theco-solvent. For instance, the method may be carried out at a temperatureof at least 30° C.

Preferably, at least one of the aqueous and non-aqueous phases comprisesan emulsifier. More preferably, the aqueous phase comprises anemulsifier. Examples of emulsifiers include, without limitation,poly(vinyl alcohol) (PVA), poly(vinyl pyrrolidone) (PVP), cetyltrimethylammonium bromide (CTAB) and mixtures thereof. In some examples,the emulsifier is present in an amount of from 0.01 to 50% by weight ofthe aqueous phase, preferably from 0.5 to 30%, and more preferably from0.1 to 10% by weight.

In some examples, the polymeric shell is formed by an interfacialpolymerisation process. For example, the polymeric shell may be preparedby an interfacial polymerisation process which involves the use of anon-aqueous phase comprising the liquid core material and one or moreoil-soluble monomers; and an aqueous phase comprising one or morewater-soluble monomers and an emulsifier. The non-aqueous and aqueousphases are emulsified to form an emulsion comprising droplets of thenon-aqueous phase dispersed within the aqueous phase. The monomers arethen polymerised, typically by heating, with polymerisation occurring atthe interface between the non-aqueous phase and the aqueous phase.

Alternatively, the polymeric shell may be obtainable by interfacialpolymerisation of a pre-polymer. Such processes may be used to prepare arange of different polymeric shell materials. For example, a polymericshell comprising a polyacrylate, polyamine or polyurea material may beprepared by such a process.

Preferably, the polymeric material comprises a polyacrylate. In someexamples, the polymeric shell comprises a polyacrylate and is obtainableby interfacial polymerisation of a pre-polymer, wherein the pre-polymeris obtained by reacting a mixture comprising: (i) an aminoalkyl acrylatemonomer, an aminoalkyl methacrylate monomer, or a mixture thereof; and(ii) an acrylate monomer, a methacrylate monomer, an acrylate oligomer,a methacrylate oligomer, or a mixture thereof.

More preferably, the polymeric shell is prepared by a processcomprising:

(i) providing a non-aqueous phase comprising the liquid core material,an amine monomer, a multifunctional acrylate or methacrylate monomer oroligomer, an acid and a free radical initiator;

(ii) reacting the amine monomer with the multifunctional acrylate ormethacrylate monomer or oligomer to form a pre-polymer;

(iii) providing an aqueous phase comprising an emulsifier, an alkali oralkali salt, and optionally a free radical initiator;

(iv) contacting the non-aqueous phase with the aqueous phase underconditions such that an emulsion is formed comprising droplets of thenon-aqueous phase dispersed in the aqueous phase; and

(v) polymerising the pre-polymer to form a polymeric shell whichencapsulates the liquid droplets.

The amine monomer is an oil-soluble or oil-dispersible amine monomer,more preferably an aminoalkyl acrylate or aminoalkyl methacrylate. Insome examples, the amine monomer is selected from aminoalkyl acrylates,alkyl aminoalkyl acrylates, dialkyl aminoalkyl acrylates, aminoalkylmethacrylates, alkylamino aminoalkyl methacrylates, dialkyl aminoalkylmethacrylates, tertiarybutyl aminoethyl methacrylates, diethylaminoethylmethacrylates, dimethylaminoethyl methacrylates, dipropylaminoethylmethacrylates, and mixtures thereof. Preferred amine monomers arediethylaminoethyl methacrylate, dimethylaminoethyl methacrylate,tert-butyl aminoethyl methacrylate, and mixtures thereof. Morepreferably, the amine is tert-butylaminoethyl methacrylate and themultifunctional acrylate or methacrylate monomer or oligomer is ahexafunctional aromatic urethane acrylate oligomer.

In the above process, an aqueous phase comprising an emulsifer and analkali or alkali salt is used. Examples of emulsifiers include, withoutlimitation, poly(vinyl alcohol) (PVA), poly(vinyl pyrrolidone) (PVP),cetyl trimethylammonium bromide (CTAB), and mixtures thereof. In someexamples, the alkali or alkali salt is sodium hydroxide.

The interfacial polymerisation process is preferably performed in thepresence of a free radical initiator. Examples of suitable free radicalinitiators include azo initiators, peroxide, alkyl peroxides, dialkylperoxides, peroxyesters, peroxycarbonates, peroxyketones andperoxydicarbonates. In some examples, the free radical initiator isselected from 2,2′-azobis-(2,4-dimethylpentanenitrile),2,2′-azobis-(2-methyl-butyronitrile), and mixtures thereof. A freeradical initiator may be present in the aqueous phase, the non-aqueousphase, or both.

In some examples, the microcapsules are prepared by an in situpolymerisation process. Such processes are known in the art andgenerally involve preparing an emulsion comprising droplets of theliquid core material dispersed in a continuous phase comprising aprecursor material which can be polymerised to form a polymeric shell;and polymerising the precursor material to form a polymeric shell,thereby encapsulating the liquid droplets. The polymerisation process issimilar to that of interfacial polymerisation processes, except in thatno precursor materials for the polymeric shell are included in theliquid core material in in situ polymerisation processes. Thus,polymerisation occurs solely in the continuous phase, rather than oneither side of the interface between the continuous phase and the corematerial.

Examples of precursor materials for the polymeric shell include, withoutlimitation, pre-polymer resins such as urea resins, melamine resins,acrylate esters, and isocyanate resins. Preferably, the polymeric shellis formed by the polymerisation of a precursor material selected from:melamine-formaldehyde resins; urea-formaldehyde resins; monomeric or lowmolecular weight polymers of methylol melamine; monomeric or lowmolecular weight polymers of dimethylol urea or methylated dimethylolurea; and partially methylated methylol melamine.

The use of melamine-formaldehyde resins or urea-formaldehyde resins asthe precursor material is particularly preferred. Procedures forpreparing microcapsules comprising from such precursor materials areknown in the art (see, e.g., U.S. Pat. No. 3,516,941, U.S. Pat. No.5,066,419 and U.S. Pat. No. 5,154,842). The capsules are made by firstemulsifying the liquid core material as small droplets in an aqueousphase comprising the melamine-formaldehyde or urea-formaldehyde resin,and then allowing the polymerisation reaction to proceed along withprecipitation at the oil-water interface.

In some examples, the microcapsules may be prepared by a processcomprising:

(i) providing a non-aqueous phase comprising the liquid core material;

(ii) providing an aqueous phase comprising a melamine-formaldehydepre-polymer (e.g. a partially methylated methylol melamine resin);

(iii) emulsifying the non-aqueous and aqueous phases to form an emulsioncomprising droplets of the non-aqueous phase dispersed in the aqueousphase; and

(iv) condensing the melamine-formaldehyde pre-polymer, thereby forming amelamine-formaldehyde polymer which precipitates from the aqueous phaseand encapsulates said droplets.

The polymerisation process is preferably performed using an emulsifier,which is preferably present in the aqueous phase. By way ofillustration, an anionic emulsifier (e.g. copolymers of butyl acrylateand acrylic acid) and/or a neutral emulsifier (e.g. PVP) may be used.

Condensation of the melamine-formaldehyde pre-polymer may be initiatedby, e.g., lowering the pH of the emulsion. The pH of the emulsion may beadjusted using a base as appropriate. Examples of suitable bases includealkali metal hydroxides (e.g. sodium hydroxide), ammonia, andtriethanolamine.

In each of the emulsification processes described herein, emulsificationcan be conducted using any suitable mixing device known in the art. Forexample, a homogeniser, colloid mill, ultrasonic dispersion device, orultrasonic emulsifier may be used. Preferably, a homogeniser is used.

The resulting polymeric shell may have a thickness of greater than 0.5nm, preferably greater than 1 nm, and more preferably greater than 2 nm.Typically, the polymeric shell will have a shell thickness of less than2000 nm, preferably less than 1500 nm, and more preferably less than1100 nm. The microcapsules preferably have a polymeric shell with athickness of from 1 to 2000 nm, such as from 2 to 1100 nm. Factors suchas the concentration of the shell-forming material in the emulsion willdictate the thickness of the polymeric shell.

The size of the microcapsules can be controlled by altering factors suchas the stirring speed and the shape of the stirring blade or rotor bladeof the stirrer or homomixer used during the emulsification step of themicroencapsulation process, or by adjusting the reaction rate byaltering the polymerisation conditions (e.g. the reaction temperatureand time) for the polymeric material. In particular, the size of themicrocapsules may be controlled by regulating the stirring speed, whichin turn regulates the size of the droplets of the liquid core materialin the emulsion.

Metallic Coating

The coated microcapsules further comprise a metallic coating whichsurrounds the microcapsules. The metallic coating comprises particles ofa first metal adsorbed on the polymeric shell and a film of a secondmetal disposed on said particles. The film of the second metal providesfor a continuous coating which surrounds the surface of themicrocapsule. Preferably the thickness of the metallic coating issubstantially uniform throughout the coating.

The particles of the first metal are preferably nanoparticles. The term“nanoparticles” as used herein refers to particles having a particlesize of from 1 to 200 nm. Preferably, the metal nanoparticles have aparticle size of less than 100 nm, e.g. less than 50 nm More preferably,the metal nanoparticles have a particle size of less than 10 nm, morepreferably less than 5 nm, and more preferably less than 3 nm. In thisregard, the use of smaller metal nanoparticles may result in theformation of a thinner metallic coating. The nanoparticles willtypically have a spheroidal geometry, but they may exist in more complexforms such as rods, stars, ellipsoids, cubes or sheets.

In some examples, the nanoparticles comprise gold, silver, copper, tin,cobalt, tungsten, platinum, palladium, nickel, iron or aluminiumnanoparticles, or mixtures thereof. In some examples, the nanoparticlescomprise an alloy of two or more metals, e.g. an alloy of two or moremetals selected from gold, silver, copper, tin, cobalt, tungsten,platinum, palladium, nickel, iron and aluminium. In some examples, thenanoparticles comprise a metal oxide, e.g. aluminium oxide or an ironoxide. In some examples, the nanoparticles comprise core-shell particlescomprising a core of a first metal or metal oxide surrounded by a shellof a second metal or metal oxide. In some examples, the nanoparticlesconsist of a single metal.

As described in more detail below, the film of the second metal ispreferably applied by an electroless plating procedure which iscatalysed by the particles of the first metal. It is therefore preferredthat the particles of the first metal comprise a metal which catalysesthe electroless plating process.

The first metal may be selected from the transition metals and p-blockmetals, e.g. a metal selected from those metals listed in Groups 9 to 14of the Periodic Table, in particular a metal selected from Groups 10, 11and 14. Preferably, the first metal is a metal selected from nickel,palladium, platinum, silver, gold, tin and combinations thereof.Preferably, the first metal comprises platinum, silver, gold, or amixture thereof.

The first and second metals may be the same or different. Preferably,the second metal is different to the first metal.

The second metal is preferably a metal that is capable of beingdeposited via an electroless plating process. The second metal may be atransition metal, e.g. a metal selected from those metals listed inGroups 9 to 14 of the Periodic Table, in particular a metal selectedfrom Groups 10 and 11. Preferably, the second metal is a metal selectedfrom silver, gold, copper and combinations thereof.

In some examples, the first metal is selected from Au, Pt, Pd, Sn, Agand combinations thereof; and the second metal is selected from Au, Ag,Cu, Ni and combinations thereof.

In some examples, the first metal is selected from Au, Pt, Pd, Sn, Agand combinations thereof (e.g. Sn/Ag) and the second metal is Au. Insome examples, the first metal is selected from Sn, Pt, Ag, Au andcombinations thereof (e.g. Pt/Sn) and the second metal is Ag. In someexamples, the first metal is selected from Sn, Ag, Ni and combinationsthereof (e.g. Sn/Ni or Sn/Ag) and the second metal is Cu. In someexamples, the first metal is selected from Sn, Pd, Ag and combinationsthereof (e.g. Sn/Pd) and the second metal is Ni.

In some examples, the first metal is Pt and the second metal is Au; thefirst metal is Au and the second metal is Ag; or the first metal is Auand the second metal is Cu. More preferably, the first metal is Au andthe second metal is Ag; or the first metal is Pt and the second metal isAu.

The particles of the first metal are preferably adsorbed onto thepolymeric shell in the form of a discontinuous layer such that, prior toapplication of the metallic film, the surface of the polymeric shellcomprises regions comprising adsorbed metal particles and regions inwhich adsorbed metal particles are absent. The metal particles may bedistributed over the surface of the polymeric shell in a substantiallyuniform manner.

The thickness of the film of the second metal may vary with the densityof the particles of the first metal that are adsorbed onto the polymericshell of the microcapsule, with a higher density of particles of thefirst metal typically encouraging the growth of a thinner film. In someexamples, the particles are deposited onto the polymeric shell at adensity such that said particles cover from 0.1 to 80% of the surfacearea of the polymeric shell, e.g. from 0.5 to 40% of the surface area ofthe polymeric shell, e.g. from 1 to 4% of the surface area of thepolymeric shell. The density of the particles on the polymeric shell maybe determined using the procedure described in the Test Methods sectionherein.

Deposition of the First Metal

The particles of the first metal are charge-stabilised nanoparticleswhich are adsorbed on the polymeric shell. Charge-stabilisednanoparticles are nanoparticles which comprise a charged speciesadsorbed on the surface thereof. Since the stabiliser is a chargedspecies, it will impart a charged surface to the nanoparticles which canbe exploited in order to adsorb the metal particles to the surface ofthe polymeric shell. Thus, in some examples, the particles of the firstmetal are adsorbed on the polymeric shell by electrostatic interaction.

The particles are preferably adsorbed on a surface-modifying agent thatforms part of the polymeric shell. The surface-modifying agent may beadsorbed on and/or absorbed within the polymeric shell. Preferably, thepolymeric shell was obtained by an emulsification process in which thesurface-modifying agent was employed as an emulsifier, with theemulsifier being retained in the resulting shell. The surface-modifyingagent preferably presents a charged surface which is used toelectrostatically attract and adsorb the charge-stabilised nanoparticleson to the polymeric shell.

In some examples, the particles of the first metal are charge-stabilisedby an anionic stabiliser. In some examples, the anionic stabiliser isselected from borohydride anions and citrate anions. In some examples,the anionic stabiliser is an anionic surfactant, e.g. an anionicsurfactant selected from sodium dodecyl sulfate, sodium laureth sulfate,dodecyl benzene sulfonic acid, perfluorooctanesulfonate, dioctyl sodiumsulfosuccinate and sodium stearate. Preferably, the particles areborohydride-stabilised or citrate-stabilised nanoparticles.

In some examples, the particles of the first metal have a zeta potentialof from −20 mV to −150 mV, e.g. from −30 mV to −90 mV.

Where the particles of the first metal are stabilised by an anionicstabiliser, it is preferable for the surface of the polymeric shell tobe neutral or cationic. In some examples, the polymeric shell has asubstantially neutral surface having a zeta potential of from −10 mV to+10 mV, e.g. from −5 mV to +5 mV. In some examples, the polymeric shellhas a positively charged surface, e.g. having a zeta potential of from+20 mV to +150 mV, e.g. from +30 mV to +90 mV.

In some examples, the particles of the first metal are stabilised by ananionic stabiliser and the polymeric shell comprises a non-ionicsurface-modifying agent. In some examples, the surface-modifying agentis a non-ionic polymer, e.g. a non-ionic polymer selected frompoly(vinyl alcohol) and poly(vinyl pyrrolidone).

In some examples, the particles of the first metal are stabilised by ananionic stabiliser and the polymeric shell comprises a cationicsurface-modifying agent. The surface-modifying agent may be a cationicsurfactant or a cationic polymer. Examples of cationic surfactantsinclude, without limitation, alkyl ammonium surfactants such as cetyltrimethylammonium bromide, dodecyl dimethylammonium bromide, cetyltrimethylammonium chloride, benzalkonium chloride, cetylpyridiniumchloride, dioctadecyl dimethylammonium chloride and dioctadecyldimethylammonium bromide. Examples of cationic polymers include, withoutlimitation, poly(diethylaminoethyl methacrylate),poly(dimethylaminoethyl methacrylate), poly(tertiarybutylaminoethylmethacrylate) and di-block copolymers formed of a first block comprisinga poly(aminoalkyl acrylate) and a second block comprising a poly(alkylacrylate). More preferably, the surface-modifying agent is cetyltrimethylammonium bromide.

Alternatively, the particles of the first metal may be charge-stabilisedby a cationic stabiliser. Examples of cationic stabilisers includecationic surfactants such as quaternary ammonium surfactants, e.g. cetyltrimethylammonium bromide, tetraoctylammonium bromide and dodecyltrimethylammonium bromide. Other quaternary ammonium surfactants includethe esterquats, i.e. quaternary ammonium surfactants containing an estergroup.

In some examples, the particles of the first metal have a zeta potentialof from +20 mV to +150 mV, e.g. from +30 mV to +90 mV.

Where the particles of the first metal are stabilised by a cationicstabiliser, it is preferable for the surface of the polymeric shell tobe neutral or anionic. In some examples, the polymeric shell has asubstantially neutral surface having a zeta potential of from −10 mV to+10 mV, e.g. from −5 mV to +5 mV. In some examples, the polymeric shellhas a positively charged surface, e.g. having a zeta potential of from−20 mV to −150 mV, e.g. from −30 mV to −90 mV.

In some examples, the particles of the first metal are stabilised by acationic stabiliser and the polymeric shell comprises a non-ionicsurface-modifying agent. In some examples, the surface-modifying agentis a non-ionic polymer, e.g. a non-ionic polymer selected frompoly(vinyl alcohol) and poly(vinylpyrrolidone).

In some examples, the particles of the first metal are stabilised by acationic stabiliser and the polymeric shell comprises an anionicsurface-modifying agent. The surface-modifying agent may be an anionicsurfactant or an anionic polymer. Examples of anionic surfactantsinclude, without limitation, sodium dodecyl sulfate, sodium laurethsulfate, dodecyl benzene sulfonic acid, dioctyl sodium sulfosuccinate,perfluorooctanesulfonate, dioctyl sodium sulfosuccinate and sodiumstearate. Examples of anionic polymers include, without limitation,polyacids such as poly(acrylic acid) and poly(methacrylic acid).

The particles of the first metal may alternatively be charge-stabilisedby a zwitterionic stabiliser. In some examples, the zwitterionicstabiliser is a zwitterionic surfactant. Examples of zwitterionicsurfactants include aminobetaines, imidazoline derivatives andphospholipids, e.g. phosphatidyl cholines.

The charge-stabilised nanoparticles may be prepared using suitableprocedures known in the art (see, e.g., G. Frens, Nature, 1973, 241,20-22). Such procedures will typically involve reducing metal ions insolution in the presence of charged stabiliser. Thus, thecharge-stabilised nanoparticles may be obtained by providing a solutioncomprising ions of the first metal and a charged stabiliser, andreducing the ions to form metal particles which are charge-stabilised bythe stabiliser.

In some examples, metal ions in solution are reduced by a reducing agentwhich becomes the charged stabiliser e.g. by sodium borohydride or bysodium citrate. By way of illustration, and without limitation,borohydride-stabilised gold nanoparticles may be prepared by contactingan aqueous solution of chloroauric acid with sodium borohydride.

The resulting charge-stabilised nanoparticles may then be contacted withuncoated microcapsules under appropriate conditions, e.g. at ambienttemperature. The microcapsules may then be washed to remove any unboundparticles.

Preferably, the ions of the first metal are present in the solution at aconcentration of from 0.005 to 50 mM, e.g. from 0.01 to 20 mM, e.g. from0.05 to 5 mM. Preferably, the charged stabiliser is present in thesolution at a concentration of from 0.005 to 50 mM, e.g. from 0.01 to 20mM, e.g. from 0.05 to 5 mM.

Deposition of the Second Metal

Once the particles of the first metal have been adsorbed onto thepolymeric shell, a film of a second metal is formed on the particles ofthe first metal, thereby coating the polymeric shell with a continuousmetallic film that surrounds the microcapsule. Preferably the thicknessof the metallic coating is substantially uniform throughout the coating.

The metallic film is preferably formed by an electroless plating processin which the deposition of the second metal is catalysed by the adsorbedparticles of the first metal. The electroless deposition process willgenerally comprise contacting microcapsules onto which particles of thefirst metal have been deposited with a solution of ions of the secondmetal in the presence of a reducing agent, in the absence of an electriccurrent. The reducing agent is typically a mild reducing agent such asformaldehyde and the electroless plating is preferably performed underalkaline conditions. Once the electroplating reaction commences, thedeposition of the metallic coating may become autocatalytic. Thethickness of the metallic film may be controlled by limiting theconcentration of the ions of the second metal in solution and/or theduration of the electroless plating procedure.

Suitable techniques for conducting the electroless plating procedure aredescribed, for example, in the following documents: Basarir et al., ACSApplied Materials & Interfaces, 2012, 4(3), 1324-1329; Blake et al.,Langmuir, 2010, 26(3), 1533-1538; Chen et al., Journal of PhysicalChemistry C, 2008, 112(24), 8870-8874; Fujiwara et al., Journal of theElectrochemical Society, 2010, 157(4), pp. D211-D216; Guo et al.,Journal of Applied Polymer Science, 2013, 127(5), 4186-4193; Haag etal., Surface and Coatings Technology, 2006, 201(6), 2166-2173; Horiuchiet al., Surface & Coatings Technology, 2010, 204(23), 3811-3817; Ko etal., Journal of the Electrochemical Society, 2010, 157(1), pp. D46-D49;Lin et al., International Journal of Hydrogen Energy, 2010, 35(14),7555-7562; Liu et al., Langmuir, 2005, 21(5), 1683-1686; Ma et al.,Applied Surface Science, 2012, 258(19), 7774-7780; Miyoshi et al.,Colloids and Surfaces A: Physicochemical and Engineering Aspects, 2008,321(1-3), 238-243; Moon et al., 2008, Ultramicroscopy, 108(10),1307-1310; Wu et al., Journal of Colloid and Interface Science, 2009,330(2), 359-366; Ye et al., Materials Letters, 2008, 62(4-5), 666-669;and Zhu et al., Surface and Coatings Technology, 2011, 205(8-9),2985-2988.

By way of illustration, and without limitation, a silver film may beprepared by forming a dispersion comprising silver nitrate,formaldehyde, ammonia and microcapsules comprising particles of thefirst metal. The dispersion is then stirred for a sufficient period oftime until a metallic film of the desired thickness is obtained. Thecapsules may then be washed, e.g. by centrifugation, in order toseparate them from the plating solution.

The ions of the second metal are preferably present in the solution at aconcentration of from 0.05 to 2000 mM, e.g. from 0.1 to 1750 mM, e.g.from 0.5 to 1500 mM. Preferably, the reducing agent is present in thesolution at a concentration of from 0.05 to 3500 mM, e.g. from 0.1 to3000 mM, e.g. from 0.5 to 2500 mM. Preferably, the second metal and thereducing agent are present in the solution at a molar ratio of secondmetal to reducing agent of from 1:10 to 4:1, e.g. from 1:5 to 2:1, e.g.from 1:3 to 1:1.

The electroless plating process may be performed at any suitabletemperature, e.g. a temperature of from 0 to 80° C. Preferably, theelectroless plating process is performed at room temperature.

Characteristics and Properties of the Coated Microcapsules

The coated microcapsules may be obtained in a range of differentparticle sizes. Preferably, the coated microcapsules have a particlesize of at least 0.1 microns, more preferably at least 1 micron.Typically, the coated microcapsules will have particle size of 500microns or less, such as 100 microns or less, and more preferably 50microns or less. Preferably, the coated microcapsules have a particlesize of from 0.1 to 500 microns, e.g. from 1 to 100 microns, e.g. from 1to 30 microns, e.g. from 1 to 20 microns. The particle size of thecoated and uncoated microcapsules may be determined using the testprocedure described in the Test Methods section herein.

The thickness of the metallic coating may be chosen such that the coatedmicrocapsules rupture and release the encapsulated liquid core materialunder particular conditions, e.g. under particular stresses. Forinstance, when the coated microcapsules comprise a perfume oil and formpart of a fragrance formulation that is worn by a user, the metalliccoating may rupture during use, e.g. due to rubbing of the skin to whichthe formulation has been applied. In this way, the perfume oil may bereleased in a controlled manner so that it is perceptible to the userfor a prolonged period of time.

Conversely, it is also desirable for the metallic coating to have aminimum thickness so as to reduce the likelihood of solvents permeatingthrough the microcapsule wall and/or the metallic coating rupturingprematurely when the coated microcapsules are stored, transported orused. This is particularly important in the case of fine fragranceformulations, which will typically comprise a polar solvent such asethanol in which the microcapsules are dispersed.

In some examples, the metallic coating has a maximum thickness of 1000nm, e.g. a maximum thickness of 500 nm, e.g. a maximum thickness of 400nm, e.g. a maximum thickness of 300 nm, e.g. a maximum thickness of 200nm, e.g. a maximum thickness of 150 nm, e.g. a maximum thickness of 100nm, e.g. a maximum thickness of 50 nm. In some examples, the metalliccoating has a minimum thickness of 1 nm, e.g. a minimum thickness of 10nm, e.g. a minimum thickness of 30 nm. In some examples, the metalliccoating has: a minimum thickness of 1 nm and a maximum thickness of 500nm; a minimum thickness of 10 nm and a maximum thickness of 300 nm; or aminimum thickness of 10 nm and a maximum thickness of 200 nm Preferably,the metallic coating has: a minimum thickness of 10 nm and a maximumthickness of 150 nm; a minimum thickness of 10 nm and a maximumthickness of 100 nm; a minimum thickness of 20 nm and a maximumthickness of 100 nm.

The coated microcapsules are designed to release their liquid corematerial when the microcapsules are ruptured. The rupture can be causedby forces applied to the shell during mechanical interactions. Themicrocapsules may have a fracture strength of from about 0.1 MPa toabout 25 MPa. The microcapsules preferably have a fracture strength ofat least 0.5 MPa. So that the microcapsules are readily friable, theypreferably have a fracture strength of less than 25 MPa, more preferablyof less than 20 MPa, more preferably of less than 15 MPa. For instance,the microcapsules may have a fracture strength of from 0.5 to 10 MPa.The fracture strength of the microcapsules may be measured according tothe Fracture Strength Test Method described in WO 2014/047496 (see pages28-30 thereof).

The coated microcapsules may be characterised in terms of theirpermeability. A coated microcapsule preferably retains more than 50% byweight of the liquid core material under the Ethanol Stability Testdescribed herein. More preferably, the coated microcapsule preferablyretains more than 70% by weight of the liquid core material, e.g. morethan 80% by weight, e.g. more than 85% by weight, e.g. more than 90% byweight, e.g. more than 95% by weight, e.g. more than 98% by weight, whentested under the Ethanol Stability Leakage Test described herein.

In some examples, the metallic coating is applied to an uncoatedmicrocapsule which would otherwise retain less than 20% by weight of itsliquid core material when tested under the Ethanol Stability LeakageTest described herein, e.g. less than 10%, e.g. less than 5%, e.g. lessthan 1%.

Formulations and Uses

The coated microcapsules will typically be formulated as a plurality ofcoated microcapsules. Thus, in one aspect, the present disclosureprovides a formulation comprising a plurality of coated microcapsules.The coated microcapsules will typically be dispersed in a solvent. Forexample, the coated microcapsules may be dispersed in water or a polarsolvent, e.g. an alcohol such as ethanol.

Preferably, the formulation comprises the coated microcapsules in anamount of at least 1% by weight of the formulation. For example, thecoated microcapsules may be present in an amount of at least 5% byweight, at least 7% by weight or at least 10% by weight of theformulation. The formulation may comprise a mixture of different coatedmicrocapsules, the mixture comprising a plurality of coatedmicrocapsules comprising a first liquid core material and a plurality ofcoated microcapsules comprising a second liquid core material.Alternatively or additionally, the formulation may comprise othermicrocapsules, e.g. uncoated microcapsules, in addition to the coatedmicrocapsules.

Preferably, at least 75%, 85% or even 90% by weight of the coatedmicrocapsules in the formulation have a particle size of from 1 micronsto 100 microns, more preferably from 1 microns to 50 microns, even morepreferably from 10 microns to 50 microns, most preferably from 1 micronsto 30 microns. Preferably, at least 75%, 85% or even 90% by weight ofthe coated microcapsules have a polymeric shell thickness of from 60 nmto 250 nm, more preferably from 80 nm to 180 nm, even more preferablyfrom 100 nm to 160 nm.

The coated microcapsules disclosed herein may be used in consumerproducts (i.e. products intended to be sold to consumers without furthermodification or processing). Non-limiting examples of consumer productsuseful herein include products for treating hair (human, dog, and/orcat), including, bleaching, coloring, dyeing, conditioning, growing,removing, retarding growth, shampooing, styling; deodorants andantiperspirants; personal cleansing; color cosmetics; products, and/ormethods relating to treating skin (human, dog, and/or cat), includingapplication of creams, lotions, and other topically applied products forconsumer use; and products and/or methods relating to orallyadministered materials for enhancing the appearance of hair, skin,and/or nails (human, dog, and/or cat); shaving; body sprays; and finefragrances like colognes and perfumes; products for treating fabrics,hard surfaces and any other surfaces in the area of fabric and homecare, including: air care, car care, dishwashing, fabric conditioning(including softening), laundry detergency, laundry and rinse additiveand/or care, hard surface cleaning and/or treatment, and other cleaningfor consumer or institutional use; products relating to disposableabsorbent and/or non-absorbent articles including adult incontinencegarments, bibs, diapers, training pants, infant and toddler care wipes;hand soaps, shampoos, lotions, oral care implements, and clothing;products such as wet or dry bath tissue, facial tissue, disposablehandkerchiefs, disposable towels, and/or wipes; products relating tocatamenial pads, incontinence pads, interlabial pads, panty liners,pessaries, sanitary napkins, tampons and tampon applicators, and/orwipes.

In particular, the present disclosure provides a fragrance formulationwhich comprises a plurality of coated microcapsules, the coatedmicrocapsules comprising a liquid core material comprising a perfumeoil. The formulation will typically comprise a polar solvent in whichthe coated microcapsules are dispersed. Preferably the polar solvent isethanol. Thus, in some examples, the present disclosure provides afragrance formulation comprising a plurality of coated microcapsulesdispersed in ethanol. More preferably, the fragrance formulation is afine fragrance formulation.

Test Methods

Test Method for Measuring the Size of the Microcapsules

The dimensions of uncoated and coated microcapsules may be measuredusing a Malvern Mastersizer Hydro 2000SM particle size analyser.Measurements are performed according to British Standard BS ISO13099-1:2012 (“Colloidal systems—Methods for zeta-potentialdetermination”).

Test Method for Measuring the Size of the Metal Particles

The dimensions of metal particles may be measured by dynamic lightscattering. Specifically, a Malvern Nano-ZS Zetasizer and FEI TecnaiTF20 field emission transmission gun electron microscopy (FEGTEM) fittedwith HAADF detector and Gatan Orius SC600A CCD camera may be used.

Test Method for Measuring the Thickness of the Polymeric Shell and theMetallic Coating

The thickness of the polymeric shell and the metallic coating may bemeasured using microtoming and FEGTEM. In order to prepare capsulecross-section samples for TEM imaging, 1% of the washed capsules arecentrifuged and redispersed in 1 mL of ethanol. The capsule samples arethen air dried and mixed with EPO FIX epoxy resin. The sample is left toharden overnight and ˜100 nm thick microtome samples are floated ontowater and set on TEM grids. FEGTEM is used to generate images of themicrotomes and the thickness of the polymeric shell and the metalliccoating may be determined using a computer program, such as Image J.

Test Method for Measuring the Adsorption Density of Metal Particles onthe Capsule Surface

Metal particle surface adsorption densities may be measured directlyfrom TEM images. Adsorption densities can be measured for small sampleboxes on the surface of the capsule. The distance from the centre of thesphere is then noted in each case. Each measurement was then correctedfor both surface curvature and halved to compensate for the transparentnature of the capsules (TEM imaging shows the metal particles on bothsides of the capsule). The size distribution of the capsules is thenused to convert the number density obtained from these images to a 2Dsurface coverage (percent).

Test Method for Measuring the Zeta Potentials of Uncoated Microcapsules,Metal Particles and Coated Microcapsules

The zeta potentials of uncoated microcapsules, the metal particles andthe coated capsules may be analysed using a Malvern nano-ZS zetasizer.Zeta potentials are measured according to British Standard BS ISO13099-1:2012 (“Colloidal systems—Methods for zeta-potentialdetermination”).

Test Method for Analysing the Chemical Composition of the CoatedMicrocapsules

The chemical composition of the coated microcapsules may be analysedusing an Oxford Instruments INCA 350 energy dispersive X-rayspectroscopy (EDX) with 80 mm X-Max SDD detector, which is installed inFEGTEM; and EDX in FEGTSEM.

Ethanol Stability Test

The Ethanol Stability Test refers to the following test procedure.

A known volume of microcapsules (coated or uncoated microcapsules) areisolated and dispersed in an aqueous solution consisting of 1 part waterto 4 parts absolute ethanol. The dispersion is heated to 40° C. After 7days at 40° C., the microcapsules are isolated from the aqueous solutionusing centrifugation at 7000 rpm for 1 minute.

The aqueous solution is then subjected to analysis using gaschromatography to determine the content of the liquid core material thathas leached from the microcapsules. Samples are assessed using a fusedsilica column of 3 m in length and 0.25 mm internal diameter, coatedwith a 0.25 mm film of 100% dimethyl polysiloxane stationary phase. Thecolumn temperature is programmed to increase from 50° C. to 300° C. at arate of 20° C. per minute. A Clarus 580 gas chromatograph is used forthe analysis.

Where the loss of liquid core material from coated microcapsules iscompared with that from uncoated microcapsules, the uncoatedmicrocapsules may be subjected to the washing steps of the coatingprocedure, to ensure that there is equivalent liquid core material lossfrom the coated and uncoated microcapsules in advance of the EthanolStability Test.

To confirm the presence of the liquid core material within the coatedmicrocapsules, a known sample of capsules is crushed between two glassslides and washed into a vial with 5 ml ethanol. The capsules areisolated from the aqueous solution using centrifugation at 7000 rpm for1 minute. The aqueous solution is then subjected to analysis using gaschromatography to determine the content of the liquid core material thathas leached from the microcapsules.

The following Examples describe and illustrate embodiments within thescope of the present invention. The Examples are given solely for thepurpose of illustration and are not to be construed as limitations ofthe present invention, as many variations thereof are possible withoutdeparting from the spirit and scope of the invention.

Unless otherwise stated, the test procedures used in these Examples arethose specified in the Test Methods section of this specification.

Example 1: Synthesis of Microcapsules Containing a Polyacrylate Shelland a Toluene Core

The following procedure was used to prepare microcapsules comprising apolyacrylate shell and a toluene core. Microcapsules were prepared by acoacervation procedure which involved oil-in-water emulsificationfollowed by solvent extraction. Cetyl trimethylammonium bromide was usedas an emulsifier.

5 g of poly(ethyl methacrylate) (PEMA, 99%, Sigma) was dissolved in 81 gof dichloromethane (DCM) (>99%, Acros Organics). 14 g of toluene (99%,Acros Organics) was added to this and mixed until one phase formed. Thisformed the “core” phase. In a 100 ml volumetric flask, a 0.28%emulsifier solution was prepared by dissolving a sufficient amount ofcetyl trimethylammonium bromide (CTAB, 98%, Sigma) in Milli-Q water, toform the “continuous” phase. 7 ml of both the “core” and “continuous”phase was added to a glass vial and emulsified using a homogeniser (IKAT25 Ultra-Turrax) at 15000 rpm for 2 min. The stabilised emulsion wasthen stirred magnetically at 400 rpm while 86 ml of the “continuous”phase was poured in slowly. The diluted emulsion was then stirred at 400rpm for 24 hours at room temperature to allow capsule formation tooccur. The capsules were isolated by washing via centrifugation (HeraeusMegafuge R16) and removing the supernatant three times at 4000 rpm for 5min. The capsules were redispersed in 25 ml Milli-Q water.

Example 2: Synthesis of Microcapsules Containing a Polyacrylate Shelland a Hexyl Salicylate Core

The following procedure was used to prepare microcapsules comprising apolyacrylate shell and a hexyl salicylate core. Microcapsules wereprepared by a coacervation procedure which involved oil-in-wateremulsification followed by solvent extraction. Poly(vinyl alcohol) wasused as an emulsifier.

10 g of poly(methyl methacrylate) (PMMA, 99%, Sigma) was dissolved in 60g of dichloromethane (DCM) (>99%, Acros Organics). 30 g of hexylsalicylate (Procter and Gamble) was added to this and mixed until onephase formed. This formed the “core” phase. In a 100 ml volumetricflask, a 0.28% emulsifier solution was prepared by dissolving asufficient amount of cetyl trimethylammonium bromide (CTAB, 98%, Sigma)in Milli-Q water, to form the “continuous” phase. 7 ml of both the“core” and “continuous” phase was added to a glass vial and emulsifiedusing a homogeniser (IKA T25 Ultra-Turrax) at 15000 rpm for 2 min. Thestabilised emulsion was then stirred magnetically at 400 rpm while 86 mlof the “continuous” phase was poured in slowly. The diluted emulsion wasthen stirred at 400 rpm for 24 hours at room temperature to allowcapsule formation to occur. The capsules were isolated by washing viacentrifugation (Heraeus Megafuge R16) and removing the supernatant threetimes at 4000 rpm for 5 min. The capsules were redispersed in 50 mlMilli-Q water.

Example 3: Preparation of Charge-Stabilised Gold Nanoparticles

The following procedure was used to prepare borohydride-stabilised goldnanoparticles.

0.34 g HAuCl₄ was dissolved in Milli-Q water in a 25 ml volumetricflask. 0.036 g HCl was dissolved in Milli-Q water in a 25 ml volumetricflask. The HAuCl₄ and HCl solutions were combined in a separate flask.1.25 ml of this was added dropwise to 47.25 ml Milli-Q water and stirredvigorously. A borohydride solution was prepared by adding 0.095 g NaBH₄dissolved in 25 ml Milli-Q water, to 0.1 g NaOH dissolved in 25 mlMilli-Q water. 1.5 ml of this was added all at once, and the solutionwas stirred for 1 minute. The solution changed colour from pale yellowto dark ruby red indicating formation of Au nanoparticles.

Example 4: Adsorption of Charge-Stabilised Gold Nanoparticles ontoMicrocapsules

The following procedure was used to adsorb the charge-stabilised goldnanoparticles of Example 3 onto the surface of the microcapsules ofExamples 1 and 2.

6 ml of the Au nanoparticles were added to a beaker and stirredvigorously. 0.5 ml microcapsules were added dropwise, and stirredvigorously for a further 10 minutes. The microcapsules were collected bycentrifuging (Heraeus Megafuge R16) and removing the supernatant fourtimes at 4000 rpm for 10 min, to remove excess nanoparticles, and werethen redispersed in water (2 ml).

Example 5: Formation of Silver Film by Electroless Plating

The following procedure was used to form a continuous silver film on themicrocapsules of Example 4 by electroless plating.

2 ml of microcapsules were added to a beaker containing 47.5 ml Milli-Qwater. 0.5 ml of 0.1M AgNO₃ (99%, Sigma) was added and stirredvigorously. Then 50 μl of formaldehyde (35% in H₂O, Sigma) was added,followed by 26 μl of ammonia (25% in H₂O, Sigma) to control the pH to˜10, giving a silver-grey dispersion. The dispersion was then stirredfor 10 min after which it was centrifuged at 4000 rpm for 10 min, 3times, for washing, replacing the supernatant each time with Milli-Qwater.

Example 6: Characterisation of Microcapsules Comprising an Au/AgMetallic Coating

Coated microcapsules comprising a PEMA shell, a toluene core and ametallic coating comprising a silver film disposed on a layer ofborohydride-stabilised gold nanoparticles were prepared following theprocedures described in Examples 1, 3, 4 and 5. The coated microcapsuleswere then characterised using optical microscopy, SEM, TEM and EDX.

FIG. 2A is an optical micrograph showing the uncoated PEMAmicrocapsules. FIGS. 2B and 2C are a TEM image showing theborohydride-stabilised gold nanoparticles adsorbed on the surface of themicrocapsules. FIG. 2D is an SEM image showing the continuous silverfilm. FIG. 2E is an EDX graph of the silver film. The maximum thicknessof the metallic coating was 140 nm in this example, but it will beappreciated that the thickness of the coating may be varied. Referenceis made in this regard to FIGS. 3A, 3B, 3C, 3D and 3E and FIG. 4, whichillustrate that the thickness of the metallic coating may be modifiedby, for example, varying the concentration of silver ions in theelectroless plating solution.

The coated microcapsules were then tested for their ability to retainthe liquid core material using the Ethanol Stability Test describedherein, and their performance was compared with that of uncoated PEMAmicrocapsules. Whereas the coated microcapsules exhibited negligibleleakage of the liquid core material, more than 50% of the liquid corematerial had leaked from the uncoated microcapsules after one day.

Example 7: Synthesis of Microcapsules Comprising a Melamine FormaldehydeShell and a Soybean Oil Core

The following procedure was used to prepare microcapsules comprising amelamine formaldehyde shell and a liquid core comprising soybean oil.Microcapsules were prepared by an in situ polymerisation process inwhich a butyl acrylate-acrylic acid copolymer and poly(vinyl alcohol)were used as emulsifiers.

0.9 g of butyl acrylate-acrylic acid copolymer (Colloid C351, 2% solids,Kemira), and 0.9 g of poly(acrylic acid) (PAA, 100 kDa, 35% in waterSigma) were dissolved in 20 g of Milli-Q water. An amount of sodiumhydroxide was added to this solution to adjust the pH to 3.5.

0.65 g of partially methylated methylol melamine resin (Cymel 385, 80%solids, Cytec) and 20 g of hexyl salicylate were added whilst mixing at1000 rpm for 60 minutes. In a separate container, 1.0 g of butylacrylate-acrylic acid copolymer was mixed with 2.5 g of partiallymethylated methylol melamine resin in 12 g of Milli-Q water. An amountof sodium hydroxide was added to this to adjust the pH to 4.6. This wasadded to the main mix along with 0.4 g of sodium sulfate (Sigma). Themixture was heated to 75° C. and the temperature maintained for 6 h withcontinuous stirring at 400 rpm.

Example 8: Synthesis of Microcapsules Comprising a Polyacrylate Shelland a Core Comprising Soybean Oil and Isopropyl Myristate

The following procedure was used to prepare microcapsules comprising apolyacrylate shell and a liquid core comprising soybean oil andisopropyl myristate. Microcapsules were prepared by an interfacialpolymerisation procedure in which poly(vinyl pyrrolidone) was used as anemulsifier.

15.0 g of hexyl acetate was mixed with 3.75 g of isopropyl myristate at400 rpm until a homogenous solution was obtained. 15.0 g of the solutionwas placed in a three-neck round-bottom flask and mixed at 1000 rpmusing a magnetic stirrer.

The temperature was increased to 35° C., then 0.06 g of2,2-azobis-2,4-dimethylpentanenitrile (Vazo-52, Du Pont) and 0.02 g of2,2-azobis(2-methylbutyronitrile) (Vazo-67, Du Pont) were added to thereactor, with a nitrogen blanket applied at 100 cm³·min⁻¹. Thetemperature was increased to 75° C. and held for 45 minutes before beingcooled to 60° C. slowly.

The remaining oil-myristate solution was mixed with 0.05 g oft-butylaminoethyl methacrylate (Sigma), 0.04 g of 2-carboxyethylacrylate (Sigma), and 1.95 g of hexafunctional aromaticurethane-acrylate oligomer (CN9161, Sartomer) at 400 rpm, untilhomogeneous. The mixture was degassed using nitrogen. At 60° C., thismixture was added to the reaction vessel and maintained at 1000 rpm at60° C. for 10 minutes, before stirring was stopped.

2.0 g of poly(diallyl dimethyl ammonium chloride) (pDADMAC, 32% active,Sigma) was dissolved in 23.6 ml Milli-Q water. 0.11 g of 20% sodiumhydroxide solution, then 0.12 g of 4,4-azobis(cyanovaleric acid)(Vazo-68 WSP, Du Pont) was added and stirred at 400 rpm until itdissolved.

The oil-monomer solution was added t to the pDADMAC solution. Mixing wasthen restarted at 1000 rpm for 60 minutes. The mixture was then heatedslowly to 75° C. and held at this temperature for 12 h with stirring at400 rpm.

Example 9: Preparation of Charge-Stabilised Gold Nanoparticles

The following procedure was used to prepare borohydride-stabilised goldnanoparticles.

0.34 g HAuCl₄ was dissolved in Milli-Q water in a 25 ml volumetricflask. 0.036 g HCl was dissolved in Milli-Q water in a 25 ml volumetricflask. The HAuCl₄ and HCl solutions were combined in a separate flask.1.25 ml of this was added dropwise to 47.25 ml Milli-Q water and stirredvigorously. A borohydride solution was prepared by adding 0.095 g NaBH₄dissolved in 25 ml Milli-Q water, to 0.1 g NaOH dissolved in 25 mlMilli-Q water. 1.5 ml of this was added all at once, and the solutionwas stirred for 1 minute. The solution changed colour from pale yellowto dark ruby red indicating formation of Au nanoparticles.

Example 10: Adsorption of Charge-Stabilised Gold Nanoparticles ontoMicrocapsules

The following procedure was used to adsorb the charge-stabilised goldnanoparticles of Example 17 onto the surface of the microcapsules ofExamples 15 and 16.

5 ml of the Au nanoparticles were added to a beaker and stirredvigorously. 2 ml microcapsules were added dropwise, and stirredvigorously for a further 10 minutes. The microcapsules were collected bycentrifuging (Heraeus Megafuge R16) and removing the supernatant fourtimes at 4000 rpm for 10 min, to remove excess nanoparticles, and werethen redispersed in water (20 ml).

Example 11: Formation of Silver Film by Electroless Plating

The following procedure was used to form a continuous silver film on themicrocapsules of Example 18 by electroless plating.

5 ml of microcapsules were added to a beaker containing 30 ml Milli-Qwater. 0.5 ml of 0.1M AgNO₃ (99%, Sigma) was added and stirredvigorously. Then 50 μl of formaldehyde (35% in H₂O, Sigma) was added,followed by 26 μl of ammonia (25% in H₂O, Sigma) to control the pH to˜10, giving a silver-grey dispersion. The dispersion was then stirredfor 10 min after which it was centrifuged at 4000 rpm for 10 min, 3times, for washing, replacing the supernatant each time with Milli-Qwater.

Example 12: Characterisation of Microcapsules Comprising a MelamineFormaldehyde Shell and an Au/Ag Metallic Coating

Coated microcapsules comprising a melamine formaldehyde shell, a soybeanoil core and a metallic coating comprising a silver film disposed on alayer of borohydride-stabilised gold nanoparticles were preparedfollowing the procedures described in Examples 15 and 17-19. The coatedmicrocapsules were then characterised using optical microscopy, SEM, TEMand EDX.

The coated microcapsules were then tested for their ability to retainthe liquid core material using the Ethanol Stability Test describedherein, and their performance was compared with that of uncoatedmelamine formaldehyde microcapsules. Whereas the coated microcapsulesexhibited negligible leakage of the liquid core material, more than 50%of the liquid core material had leaked from the uncoated microcapsulesafter one day.

Example 13: Characterisation of Microcapsules Comprising a PolyacrylateShell and an Au/Ag Metallic Coating

Coated microcapsules comprising a polyacrylate shell, a core containinghexyl acetate and isopropyl myristate, and a metallic coating comprisinga silver film disposed on a layer of borohydride-stabilised goldnanoparticles were prepared following the procedures described inExamples 15-19. The coated microcapsules were then characterised usingoptical microscopy, SEM, TEM and EDX.

The coated microcapsules were then tested for their ability to retainthe liquid core material using the Ethanol Stability Test describedherein, and their performance was compared with that of uncoatedpolyacrylate microcapsules. Whereas the coated microcapsules exhibitednegligible leakage of the liquid core material, more than 50% of theliquid core material had leaked from the uncoated microcapsules afterone day.

All percentages, parts and ratios recited herein are calculated byweight unless otherwise indicated. All percentages, parts and ratios arecalculated based on the total composition unless otherwise indicated.Unless otherwise noted, all component or composition levels are inreference to the active portion of that component or composition, andare exclusive of impurities, for example residual solvents orby-products which may be present in commercially available sources ofsuch components or compositions.

It should be understood that every maximum numerical limitation giventhroughout this specification includes every lower numerical limitation,as if such lower numerical limitations were expressly written herein.Every minimum numerical limitation given throughout this specificationwill include every higher numerical limitation, as if such highernumerical limitations were expressly written herein. Every numericalrange given throughout this specification will include every narrowernumerical range that falls within such broader numerical range, as ifsuch narrower numerical ranges were all expressly written herein.

The dimensions and values disclosed herein are not to be understood asbeing strictly limited to the exact numerical values recited. Instead,unless otherwise specified, each such dimension is intended to mean boththe recited value and a functionally equivalent range surrounding thatvalue. For example, a dimension disclosed as “40 mm” is intended to mean“about 40 mm”.

Every document cited herein, including any cross referenced or relatedpatent or application and any patent application or patent to which thisapplication claims priority or benefit thereof, is hereby incorporatedherein by reference in its entirety unless expressly excluded orotherwise limited. The citation of any document is not an admission thatit is prior art with respect to any invention disclosed or claimedherein or that it alone, or in any combination with any other referenceor references, teaches, suggests or discloses any such invention.Further, to the extent that any meaning or definition of a term in thisdocument conflicts with any meaning or definition of the same term in adocument incorporated by reference, the meaning or definition assignedto that term in this document shall govern.

While particular embodiments of the present invention have beenillustrated and described, it would be obvious to those skilled in theart that various other changes and modifications can be made withoutdeparting from the spirit and scope of the invention. It is thereforeintended to cover in the appended claims all such changes andmodifications that are within the scope of this invention.

What is claimed is:
 1. A coated microcapsule comprising: a microcapsulecomprising a polymeric shell and a liquid core material encapsulatedtherein; and a metallic coating surrounding said microcapsule, whereinthe metallic coating comprises nanoparticles of a first metal adsorbedon said polymeric shell to form a discontinuous layer and a continuousfilm of a second metal overlaid thereon; wherein said nanoparticles ofthe first metal are charge-stabilised nanoparticles.
 2. A coatedmicrocapsule according to claim 1 wherein said particles are adsorbed onthe polymeric shell by electrostatic interaction.
 3. A coatedmicrocapsule according to claim 1, wherein the polymeric shell comprisesa surface-modifying agent on which at least some of said particles areadsorbed, wherein the surface modifying agent is a polymer or asurfactant.
 4. A coated microcapsule according to claim 1, wherein saidparticles are charge-stabilised by an anionic stabiliser.
 5. A coatedmicrocapsule according to claim 4, wherein the anionic stabiliser isselected from borohydride anions and citrate ions.
 6. A coatedmicrocapsule according to claim 4, wherein the anionic stabiliser is ananionic surfactant, wherein the anionic surfactant selected from sodiumdodecyl sulfate, sodium laureth sulfate, dodecyl benzene sulfonic acid,perfluorooctanesulfonate, dioctyl sodium sulfosuccinate and sodiumstearate.
 7. A coated microcapsule according to claim 4, wherein thepolymeric shell comprises a cationic surface-modifying agent, whereinthe cationic surface-modifying agent is a cationic surfactant or acationic polymer.
 8. A coated microcapsule according to claim 7, whereinsaid cationic surface-modifying agent is a cationic surfactant selectedfrom cetyl trimethylammonium bromide, dodecyl dimethylammonium bromide,cetyl trimethylammonium chloride, benzalkonium chloride, cetylpyridiniumchloride, dioctadecyl dimethylammonium chloride and dioctadecyldimethylammonium bromide.
 9. A coated microcapsule according to claim 8,wherein said cationic surface-modifying agent is cetyl trimethylammoniumbromide.
 10. A coated microcapsule according to claim 4, wherein thepolymeric shell comprises a non-ionic surface modifying agent, whereinthe non-ionic surface modifying agent is a non-ionic polymer, andwherein the non-ionic polymer is selected from poly(vinyl alcohol),poly(vinyl pyrrolidone), and combination thereof.
 11. A coatedmicrocapsule according to claim 1, wherein said particles arecharge-stabilised by a cationic stabiliser.
 12. A coated microcapsuleaccording to claim 11, wherein said cationic stabiliser is a cationicsurfactant, wherein the cationic surfactant is selected from cetyltrimethylammonium bromide, tetraoctylammonium bromide, dodecyltrimethylammonium bromide, and combinations thereof.
 13. A coatedmicrocapsule according to claim 12, wherein the polymeric shellcomprises an anionic surface-modifying agent, wherein the anionicsurface-modifying agent is an anionic surfactant or an anionic polymer.14. A coated microcapsule according to claim 13, wherein said anionicsurface-modifying agent is: (i) an anionic surfactant selected fromsodium dodecyl sulfate, sodium laureth sulfate, dodecyl benzene sulfonicacid, dioctyl sodium sulfosuccinate, perfluorooctanesulfonate, dioctylsodium sulfosuccinate and sodium stearate; or (ii) an anionic polymerselected from poly(acrylic acid) and poly(methacrylic acid).
 15. Acoated microcapsule according to claim 11, wherein the polymeric shellcomprises a non-ionic surface modifying agent.
 16. A coated microcapsuleaccording to claim 12, wherein the polymeric shell comprises a non-ionicsurface modifying agent, wherein the non-ionic surface modifying agent sa non-ionic polymer, and wherein the non-ionic polymer is selected frompoly(vinyl alcohol), poly(vinyl pyrrolidone), or combination thereof.17. A coated microcapsule according to claim 1, wherein: i) thecharge-stabilised nanoparticles have a particle size of less than 100nm; ii) the first metal is selected from palladium, platinum, silver,gold, nickel, tin and combinations thereof; and iii) the second metal isselected from silver, gold, copper, nickel, and combinations thereof.18. A coated microcapsule according to claim 1, wherein: i) thecharge-stabilised nanoparticles have a particle size of less than 100nm; ii) (a) the first metal is platinum and the second metal is gold;(b) the first metal is gold and the second metal is silver; or (c) thefirst metal is gold and the second metal is copper.
 19. A coatedmicrocapsule according to claim 1, wherein the metallic coating has amaximum thickness of 1000 nm, and a minimum thickness of 5 nm, andwherein the coated microcapsule has a particle size of from 0.5 micronto 500 microns.
 20. A coated microcapsule according to claim 1, whereinthe polymeric shell comprises a polyacrylate.